Let's be real, the biggest pitfall is making the Reader a passive observer. Rick would despise that. The attraction, if there is one, lies in the Reader pushing back. Not necessarily on science, but on his nihilism. Give your Reader a stupid, stubborn principle he can't just portal away from—something about community, or loyalty, or caring for a specific pet. His genius becomes a tool for the most mundane, irritatingly human problem they present. The comedy is him grumbling through a solution, and the tension is whether his corrosive worldview or their naive persistence wins out in a given scene. It's a battle of philosophies disguised as banter.
Structurally, I'd avoid a grand cosmic plot at first. Start small and weird. Maybe the Reader accidentally brews a tea that interacts with his cybernetic enhancements, or they're the only one in the city whose DNA doesn't react to a particular anomaly, making them a temporary 'control specimen' he's stuck observing. The intimacy comes from forced proximity in bizarre circumstances, not from declaring feelings. The narrative voice should be sharp, matching his chaotic energy, not dreamy. If the Reader's internal monogue sounds awed, you've lost. It should sound exasperated, fascinated against their will, and vaguely alarmed.